It’s official, there are no more free rides for smartphone data users. AT&T is phasing out its unlimited data plans (for new customers), and now Skype, just days after rolling out its first 3G friendly application will go from free to paid (sort of, anyway).

Skype confirmed that it’s free Skype to Skype VoIP calling service over 3G networks will cease being free at the end of the year. The 2.0 Skype iPhone application has been downloaded near 5m times since its release Sunday.

Right now, customers using the application are able to bypass cellular voice networks and make calls to fellow Skype users using the 3G data connection for free. The prior Skype application only connected the internet based calls over WiFi networks.

The new version makes it possible to make internet calls from virtually anywhere…at least until the end of 2010. At that point Skype will begin charging a “small” fee. For iPhone users non grandfathered into unlimited data plans that could mean a double whammy come billing time – a data fee to AT&T for using the 3G service, and a small fee to Skype for making an internet call through its 3G switchbox.

Skype says the charge is necessary to fund infrastructure costs.

The change isn’t likely to have much impact on most users — WiFi Skype to Skype calling (which is more widely used) will remain free.